After five years of planning and negotiations to build a new passenger terminal, Burbank Airport authorities have been forced to begin searching for another site for it because of a federal government ruling that their plans would place crowds of airline passengers too close to Lockheed Corp.'s secret "Skunk Works."

Last week's decision was another blow to plans for the terminal, which suffered a setback in September when a ruling by the California Supreme Court undercut the airport authority's ability to raise money for the project.

The project must proceed, however, because the current terminal, built 55 years ago, is too close to the runways to meet modern safety regulations of the Federal Aviation Administration, airport spokesman Victor Gill said.

Preliminary estimates were that the new terminal, twice the size of the existing one, would be completed in the early 1990s, but the site problem "definitely sets it back in time," Gill said. He would not estimate the length of the delay.

'Contractual Commitments'

The Burbank-Glendale-Pasadena Airport Authority announced that the proposed site for the terminal "is currently impractical" because of "contractual commitments which involve security constraints on a national level."

Those commitments bind Lockheed Corp., which owns the proposed terminal site--about 38 acres along San Fernando Boulevard on the east side of the north-south runway--according to Gill and a spokesmen for Lockheed.

Lockheed does secret work on military aircraft in an operation that has been nicknamed the Skunk Works since World War II. Lockheed owned the airfield from 1940 to 1978 and still has facilities on land around it.

The airport authority announced that, although the Lockheed site remains the desired location, airport staff members have been instructed to look for another home for the terminal. The alternatives include a site at the northwestern corner of the airport that has been backed by San Fernando Valley homeowner groups, which argue that such a location would reduce aircraft noise in the Valley.

More Negotiations Pointless

David Crowther, vice president of communications for Lockheed Corp., said further negotiations to turn over the company's land to the airport authority had become pointless because of a ruling by "a Lockheed customer" in the federal government. The ruling was that Lockheed would violate security provisions of its contract if it allowed the proposed terminal to be built close to buildings where highly secret defense work is done.

Crowther would not identify the customer, but most Lockheed aircraft projects are carried out for the Air Force.

Although talks with the airport authority about the site have been going on for some time, he said, Lockheed's operations in the area changed, bringing on the security conflict. "The use of that facility evolved into something rather different than it was when these discussions began a matter of years ago," he said.

Lockheed discussed the security aspects of the terminal plans with federal authorities "for some time, but they finally brought the hammer down . . . quite recently," he said.

Gill said the problem came up within the past three weeks.

Gill and Crowther said they did not know how close the terminal would have been to areas where classified work is carried out. "It was close enough to be unacceptable," Crowther said.

Faced with the government's security stand, Lockheed would either have to move its Burbank facility or abandon the defense contracting business if it wanted to sell or lease the land to the airport, Crowther said. Both alternatives are economically unfeasible, he said.

Classified Work

Although much secret Lockheed work has been moved to an Air Force base at Palmdale and a new research facility near Saugus, the Burbank plant continues to carry out a significant amount of "highly classified work . . . that we expect to remain there indefinitely," Crowther said.

The Skunk Works is one of the most secret and technically advanced centers in the aerospace industry. Some reports, which neither the Defense Department nor Lockheed will discuss, have said that Lockheed is developing "stealth" aircraft that will be difficult for enemy radar to detect.

The company also has announced ambitious plans to design fighter planes for the 21st Century and build the largest private aerospace research center in the world.

The name Skunk Works was taken from the illegal, secret distillery for Kickapoo joy juice in the comic strip "L'il Abner," which was popular during World War II, when Lockheed designers were working on a secret jet fighter.

Airport authorities will consider other terminal sites at the airport and on land the airport does not own, Gill said.